High density lipoproteins while lowering

All lipoprotein classes contain proteins, free and esterified cholesterol, TG and phospholipids however, the relative proportion of any component varies so that protein and phospholipid percentages are higher in a-lipoproteins (high-density lipoproteins) and lower in chylomicrons. The reverse is true for TG, while cholesterol circulates mainly as -lipoprotein (low-density lipoprotein). Since lipids circulate as lipoproteins, hyperlipaemias can be more properly defined as hyper-lipoproteinaemias. A classification of human hyperlipoproteinaemias based on chemical determination of plasma lipid classes as well as on paper electrophoretic separation of plasma lipoproteins has been proposed... 

The role of the antioxidant properties of vitamins C, E, and p-carotene in the prevention of cardiovascular disease has been the focus of several recent studies. Antioxidants reduce the oxidation of low-density lipoproteins, which may play a role in the prevention of atherosclerosis. However, an inverse relationship between the intake or plasma levels of these vitamins and the incidence of coronary heart disease has been found in only a few epidemiological studies. One study showed that antioxidants lowered the level of high-density lipoprotein 2 and interfered with the effects of lipid-altering therapies given at the same time. While many groups recommend a varied diet rich in fruits and vegetables for the prevention of coronary artery disease, empirical data do not exist to recommend antioxidant supplementation for the prevention of coronary disease. 

Fig. 2 shows the partition coefficients of three lipoproteins and three serum proteins plotted on a logarithmic scale against the pH of 16% PEG 1000-12.5% potassium phosphate buffer. The partition coefficients of serum proteins and very-low-density lipoprotein (VLDL) show an increase from 6.8 to 9.2 with increased pH, while those of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) display quite different trends, i.e., they become less than 1.0 at pH 9.2, indicating that these lipoproteins are mainly distributed in the potassium phosphate-rich lower phase at high pH. 

The main carriers of blood cholesterol are low-density lipoproteins (LDLs). LDLs, also called bad cholesterol, have a density of 1.04 g/cm. They are bad because they tend to deposit cholesterol on arterial walls, increasing the risk of stroke and heart attack. Cholesterol is also carried by high-density lipoproteins (HDLs). HDLs, also called good cholesterol, have a density of 1.13 g/cm. HDLs transport cholesterol to the liver for processing and excretion and therefore have a tendency to reduce cholesterol on arterial walls. Too low a level of HDLs (below 35 mg/100 mL) is considered a risk factor for heart disease. Exercise, along with a diet low in saturated fats, is believed to raise HDL levels in the blood while lowering LDL levels. 

Blood lipid profiles were measured during the studies and consisted of total cholesterol, high-density lipoprotein cholesterol (HDL), very low-density lipoprotein cholesterol (VLDL), low-density lipoprotein cholesterol (LDL), and triglycerides. In HMB-supplemented snbjects, HDL cholesterol showed no change, while in the placebo-supplemented subjects, a 4% increase in HDL cholesterol was seen (p < 0.04). Of particnlar interest is that supplemental HMB significantly (p < 0.03) lowered total cholesterol by 3.7% in all snbjects and by 5.8% in subjects with cholesterol levels over 200 mg/dl. The decrease in total cholesterol with HMB supplementation was mainly the result of a significant decrease in LDL cholesterol... 

In view of the fact that pectin lowers serum cholesterol levels and cholesterol Is carried by lipoproteins In the serum, we investigated the Interaction of pectin obtained from grapefruit albedo with various human serum lipoprotein fractions in vitro (22). It was observed that pectin Interacted specifically with LDL, while no Interaction was observed between pectin and high density or very low density lipoproteins. The biological significance of this observed in vitro Interaction of pectin with LDL remain unclear, primarily because of lack of evidence suggesting entry of pectin or some component of It into the blood streatm. Therefore, unless such entry and/or absorption of pectin or one of Its components is demonstrated, the biological Implication of this observed Interaction... 

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